What's the best data type for a 1 character code column in a SQL table?

Question

this is not a primary key, but merely used as a marker in existing system that marks these items with a 1 letter code ie 'N' for new, 'R' for return, etc. I was going to go with a varchar(50) as the data type but wondering if there's anything wrong with say varchar(2) instead aiming for efficiency. thx!

Answer 1

The best datatype would be char(1).

varchar means variable width, that is, if on a varchar(50) you store only 3 characters, there will be no 47 wasted bytes. But there is a (small) performance hit on accessing it as it has to go check the actual length of the field for each row.

If the requirement changes later you can alter table and modify the datatype without much trouble.